According to the Telegram channel, you should be on EMUI 9 or 9.1 before flashing the AOSP 10 rom.Tried flashing the Android 10 GSI that was recently in the XDA feed since there was an Honor View 10 running the rom...
I reverted my phone back to EMUI 8.2 using e-recovery, and flashed the image through fastboot. The android logo popped up, but after a few minutes, the phone restarted itself back to the e-recovery screen recommending a factory/reset or recovery.
Hope others can try, especially those who are on EMUI 9 or those who know how to tinker with TWRP.
EDIT:
Updated to EMUI 9... Now, the android logo doesn't boot at all and the phone is restarting on itself before it goes back to eRecovery.
"Just flash the rom and then do a factory reset and it will boot" from other user